CHEMICAL RETARDANTS At times, plants may grow too tall and open to be pleasing to customers. In these cases, chemicals are used to retard the growth of the plants, causing them to be shorter and more compact. Not only are these plants more attractive, but the shorter stems are better able to support the flowers, thereby reducing the need for staking or tying. Today, chemical retardants (chemicals which retard, or slow down growth) are used commercially as a normal part of the growing process of many plants.
Figure 5-4 illustrates the effects of various retardants. All of the chrysanthemums in the photograph are of the same variety and age. Number 1, the test plant, was not treated with a growthretarding chemical. The other four plants were treated with 8 milligrams of different test compounds. Number 2 was treated with AMO-1618; Number 3 (which shows no dwarfing effect) with
CIPC; Number 4 (which shows damage) with a carbonate; and Number 5 with phosphor.
Numbers 2 and 5 are saleable plants requiring no staking or support. Another chemical not used in this experiment, B-Nine, is used on a large scale for dwarfing potted plants.
As another example of the effect of a chemical retardant, examine the two holly plants in figure 5-5. The plant on the right has been treated with the growth regulator phosphor. The plant on the left was not treated. The treated plant is not only shorter in growth, but also has produced berries at an earlier age. This early berry production creates a more attractive plant, which sells better.
One of the newest uses of plant growth retardants is the application of a chemical to retard lawn grass growth. If applied at first “green-up” of grass in the spring, a chemical called “Limit” is absorbed by the roots and restricts grass growth for six to eight weeks. Another material called
“Embark” is leaf-absorbed and also restricts grass growth.
Another use of retardants in the vegetable industry has proven valuable. Scientists at
Pennsylvania State University experimented with soaking tomato seeds in a gel containing a growth retardant. The purpose was to keep the tomato plants from becoming too tail and spindly.
The results were a 25 percent reduction in height and more vigorous plants, which remained compact until planted in the field. When the roots grew into soil not saturated with the chemical retardant, growth returned to normal. No reduction in yield resulted in this treatment and a compact, vigorous, easy-co-handle plant resulted.
A new plant growth regulator called Sumagic reduces die height of plants by inhibiting the natural production of the plant hormone gibberellic acid. Gibberellic acid causes stems to elongate or lengthen. This chemical is taken up by the leaves, stem, and roots and moves through the plant to the growing point where it inhibits the production of gibberellic acid.
Georgia CTAE Resource Network Unit Plan Resource Unit FS-2.8 Cloze Reading • Page 1 of 3

Handout
Fill in the blanks with the most appropriate and accurate word.
CHEMICAL RETARDANTS At times, plants may grow too tall and open to be pleasing to customers. In these cases, _________ are used to retard the _________ of the plants, causing them to be _________ and more compact. Not only are these plants more _________, but the shorter stems are better able to _________ the flowers, reducing the need for __________ or tying. Today, chemical _________ (chemicals which retard, or _________ down growth) are used
_________ as a normal part of the growing process of_________ plants.
Figure 5-4 illustrates the effects of various retardants. All of the _________ in the photograph are of the same variety and age. _________ 1, the test plant, was not treated with a ________retarding chemical. The other________ plants were treated with _________ milligrams of different test compounds. Number 2 was treated with AMO-1618; Number 3 (which shows no
_________ effect) with __________; Number 4 (which shows 9 with a carbonate); and ________
5 with _________. Numbers 2 and 5 are saleable plants, requiring no staking or ________.
Another chemical not used in this ___________, B-Nine, is used on a large scale for dwarfing
_________ plants.
As another example of the effect of a chemical retardant, examine the two holly plants in figure
5-5. The plant on the right has been ________ with the growth regulator _____________. The plant on the _________ was not treated. The treated ________ is not only _________ in growth, but also has produced _________ at an earlier age. This early berry production _________ a more attractive plant which ____________ better.
One of the _________ uses of plant growth retardant is the ___________ of a chemical to retard lawn _________ growth. If applied at first “_________” of grass in the spring, a chemical called “_________” is absorbed by the roots and _____________ grass growth for six to
_________ weeks. Another material called “Embark” is leaf-absorbed and also restricts grass growth.
Georgia CTAE Resource Network Unit Plan Resource Unit FS-2.8 Cloze Reading • Page 2 of 3

Handout - Teacher's Guide
Fill in the blanks with the most appropriate and accurate word.
CHEMICAL RETARDANTS At times, plants may grow too tall and open to be pleasing to customers. In these cases, chemicals are used to retard the growth of the plants, causing them to be shorter and more compact. Not only are these plants more attractive, but the shorter stems are better able to support the flowers, reducing the need for staking or tying. Today, chemical retardants (chemicals which retard, or slow down growth) are used commercially as a normal part of the growing process of many plants.
Figure 5-4 illustrates the effects of various retardants. All of the chrysanthemum in the photograph are of the same variety and age. Number 1, the test plant, was not treated with a growth retarding chemical. The other four plants were treated with 8 milligrams of different test compounds. Number 2 was treated with AMO-1618; Number 3 (which shows no dwarfing effect) with carbonate; Number 4 (which shows 9 with a carbonate); and Number 5 with phosphor.
Numbers 2 and 5 are saleable plants, requiring no staking or support. Another chemical not used in this experiment, B-Nine, is used on a large scale for dwarfing potted plants.
As another example of the effect of a chemical retardant, examine the two holly plants in Figure
5-5. The plant on the right has been treated with the growth regulator phosphor. The plant on the left was not treated. The treated plant is not only shorter in growth, but also has produced berries at an earlier age. This early berry production creates a more attractive plant, which sells better.
One of the newest uses of plant growth retardant is the application of a chemical to retard lawn grass growth. If applied at first "green-up" of grass in the spring, a chemical called "Limit" is absorbed by the roots and resists grass growth for six to eight weeks. Another material called
"Embark" is leaf absorbed and also restricts grass growth.
Georgia CTAE Resource Network Unit Plan Resource Unit FS-2.8 Cloze Reading • Page 3 of 3